Sheet having powder coated thereon, and production and use thereof

ABSTRACT

The invention provides a sheet coated with a powdery coating composition comprising a substrate and a porous and continuous resin layer provided on the substrate, the resin layer comprising particles of the powdery coating composition having an average particle diameter of 0.1 to 30 μm and inorganic fine particles having an average particle diameter of 1 nm to 1 μm and dispersed between the particles of powdery coating composition to form space at least in part therebetween. The sheet is suitably used as an image-receiving sheet for an ink-jet recording. 
     The sheet can be obtained according to the invention by mixing a powdery coating composition having an average particle diameter of 0.1 to 30 μm with inorganic fine particles having an average particle diameter of 1 nm to 1 μm to form a powdery mixture, dry-coating the powdery mixture on a substrate, melting the powdery coating composition by heating, and fixing the coating composition together with the inorganic fine particles on the substrate to form a resin layer comprised of the powdery coating composition.

FIELD OF THE INVENTION

The present invention relates to a sheet coated with a powdery coatingcomposition, and its production and use. More particularly, it relatesto a sheet coated with a powdery coating composition, comprising asubstrate and, a porous and continuous resin layer comprising particlesof a powdery coating composition with space therebetween provided on thesubstrate, and its production and use particularly as an image-receivingsheet for a water based ink-jet recording.

DESCRIPTION OF PRIOR ART

Various recording systems have hitherto been known, and there has widelybeen used a water based ink-jet recording system for ejecting inkdirectly through a nozzle towards an image-receiving sheet, thereby toadhere ink and to record an image, recently.

This image-receiving sheet for a water based ink-jet recording hashitherto been formed by wet-coating a solution prepared by mixing awater-soluble or water-swelling resin, an inorganic pigment (such assilica) and other additives, on a substrate, drying the solution therebyto form a resin layer on the substrate, to disperse the inorganicpigment in the resin layer and to form a porous resin layer containingmicropores therein. When the image-receiving sheet receives water basedink-jet ink, the ink is absorbed both in the micropores and resinthereby to form an image on the image-receiving sheet. In such way, ahigh-quality recording image could have hitherto been obtained by anink-jet recording system using a specially prepared image-receivingsheet.

In such a specially prepared exclusive image-receiving sheet, however,an ink-receiving layer is formed by wet-coating a resin and otheradditives on a substrate, and hence, an environmental consideration isrequired on removal of the solvent. Furthermore, the resin to be used islimited as described above and the resulting image-receiving sheet isexpensive because of many production processes and the use of an organicsolvent.

The present inventors have intensively researched the production of animage-receiving sheet for an ink-jet recording by dry-coating of apowdery coating composition, not wet-coating. As a result, they havefound that, it is possible to form, on a substrate, a porous andcontinuous resin layer comprising particles of a powdery coatingcomposition and inorganic fine particles dispersed between the particlesto form space at least in part between the particles of the powderycoating composition so that the particles of the powdery coatingcomposition are apparently isolated at least in part from each other bythe inorganic fine particles by mixing the powdery coating compositionwith the inorganic fine particles in a predetermined ratio to form apowdery mixture, coating the powdery mixture on the substrate, meltingthe coated powdery mixture by heating and fixing it.

The present inventors have found that such an image-receiving sheet foran ink-jet recording having a resin layer as an ink-receiving layer canbe produced simply at low cost by using any resin with no restriction.Moreover, such an image-receiving sheet for an ink-jet recording issuperior in permeability and absorbency of jet printing ink and a clearimage having high density is formed by the image-receiving sheet for anink-jet recording, thereby making it possible to obtain a high qualityink-jet recording image. Thus, the present invention has beenaccomplished.

Therefore, it is an object of the present invention to provide a sheetcoated with a powdery coating composition whose resin layer on asubstrate has a specific structure, a method for the production and usethereof, particularly an image-receiving sheet for an ink-jet recording.

Furthermore, the present inventors have found that it is possible toobtain an image-receiving sheet for an ink-jet recording, capable offorming a clearer and more accurate image having higher density, byforming on a substrate a porous and continuous resin layer composed ofparticles of a powdery coating composition and a first inorganic fineparticles dispersed between the particles to form space at least in partbetween the particles of the powdery coating composition, and furtherforming a surface layer composed of a second inorganic fine particles onthe resin layer. Thus, the present invention has been accomplished.

It is a further object of the invention, therefore, to provide animage-receiving sheet for an ink-jet recording, capable of forming aclear and accurate image having high density, which comprises asubstrate and, a porous and continuous resin layer provided on thesubstrate, the resin layer comprising particles of a powdery coatingcomposition and a first inorganic fine particles dispersed between theparticles and forming space at least in part between the particles ofthe powdery coating composition, the sheet further comprising a surfacelayer comprising a second inorganic fine particles on the resin layer,and its production.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a sheet coatedwith a powdery coating composition, comprising a substrate and a porousand continuous resin layer provided on the substrate, the resin layercomprising particles of the powdery coating composition having anaverage particle diameter of 0.1 to 30 μm and inorganic fine particleshaving an average particle diameter of 1 nm to 1 μm dispersed betweenthe particles of the powdery coating composition and forming space atleast in part between the particles of the powdery coating composition.

Such a sheet coated with a powdery coating composition of the inventioncan be suitably used as an image-receiving sheet for an ink-jetrecording.

Such a sheet coated with a powdery coating composition can be obtainedby mixing a powdery coating composition having an average particlediameter of 0.1 to 30 μm with inorganic fine particles having an averageparticle diameter of 1 nm to 1 μm to form a powdery mixture, dry-coatingthe powdery mixture on a substrate, melting the powdery coatingcomposition by heating, and fixing the melted powdery coatingcomposition on the substrate together with the inorganic fine particlesto form a resin layer having at least in part space between theparticles of the powdery coating composition, in accordance with theinvention.

Further according to the invention, there is provided an image-receivingsheet for an ink-jet recording, comprising a resin layer having athickness of 1 to 100 μm and a surface layer comprising inorganic fineparticles having an average particle diameter of 1 to 50 nm formed onthe resin layer, the resin layer comprising particles of a powderycoating composition having an average particle diameter of 0.1 to 30 μmand containing a resin and a colorant.

Such an image-receiving sheet for an ink-jet recording can be obtainedby a method comprising the steps of dry-coating particles of a powderycoating composition having an average particle diameter of 0.1 to 30 μmand containing a resin and a colorant, on a substrate to form a resinlayer, forming a surface layer comprising inorganic fine particleshaving an average particle diameter of 1 to 50 nm on the resin layer,fixing the resin layer on the substrate, and fixing the surface layer onthe resin layer.

Particularly, a preferred image-receiving sheet for an ink-jet recordingaccording to the invention comprises a substrate and, a porous andcontinuous resin layer provided on the substrate, the resin layercomprising particles of a powdery coating composition having an averageparticle diameter of 0.1 to 30 μm and containing a resin and a colorant,and a first inorganic fine particles having an average particle diameterof 1 nm to 1 μm dispersed between the particles of the powdery coatingcomposition to form at least in part space therebetween, the sheetfurther comprising a surface layer comprising a second inorganic fineparticles having an average particle diameter of 1 to 50 nm on the resinlayer.

Such an image-receiving sheet for an ink-jet recording can be obtainedby mixing a powdery coating composition having an average particlediameter of 0.1 to 30 μm, which contains a resin and a colorant, with afirst inorganic fine particles having an average particle diameter of 1nm to 1 μm to form a powdery mixture, dry-coating the powdery mixture ona substrate to form a resin layer, and forming a surface layercomprising a second inorganic fine particles on the resin layer.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a partially sectioned perspective view showing schematicallyone embodiment of a powdery coating composition used in the invention.

FIG. 2 is a schematic view showing a section of one preferred embodimentof a sheet coated with the powdery coating composition according to theinvention.

FIG. 3 is a schematic view showing the constitution of a device forproducing the sheet coated with the powdery coating compositionaccording to the invention.

FIG. 4 is a schematic view showing a section of one preferred embodimentof an image-receiving sheet for an ink-jet recording according to theinvention.

FIG. 5 is a transmission electron micrograph showing the structure ofpowdery coating composition particles in a resin layer as one embodimentof the sheet coated with the powdery coating composition according tothe invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The sheet coated with a powdery coating composition according to theinvention comprises a substrate and, a porous and continuous resin layerprovided on the substrate, the resin layer comprising particles of apowdery coating composition having an average particle diameter (averagevalue of primary particle diameter, the same rule appliescorrespondingly to the following) of 0.1 to 30 μm and inorganic fineparticles having an average particle diameter (average value of primaryparticle diameter, the same rule applies correspondingly to thefollowing) of 1 nm to 1 μm dispersed between the particles of powderycoating composition to form space at least in part therebetween.

First, the production of the sheet coated with a powdery coatingcomposition of the invention will be described.

The sheet can be obtained by mixing a powdery coating composition havingan average particle diameter of 0.1 to 30 μm, preferably 1 to 25 μm,with inorganic fine particles having an average particle diameter of 1nm to 1 μm to form a powdery mixture, dry-coating the powdery mixture ona substrate, melting the powdery coating composition by heating andfixing the melted powdery coating composition together with theinorganic fine particles on the substrate thereby forming a porous andcontinuous resin layer on the substrate comprising the particles ofpowdery coating composition and the inorganic fine particles dispersedbetween the particles of powdery coating composition to form space atleast in part therebetween.

According to the invention, as described above, the inorganic fineparticles are adhered on the surface of particles of the powdery coatingcomposition by mixing the powdery coating composition with the inorganicfine particles, thereby making it possible to obtain a powdery mixturewherein the surface of the particles of the powdery coating compositionis coated with the inorganic fine particles.

Paper, synthetic paper and synthetic resin sheets can be preferably usedas a substrate. If necessary, a substrate made of metal is also used.Paper is not specifically limited as far as it is made of normalcellulose fibers, and includes wood free paper and coated paper, inaddition to ordinary paper. The ordinary paper includes, for example,normal PPC copying paper, those which are subjected to a calenderingtreatment to enhance the surface smoothness of the PPC copying paper,and word processor paper for heat transfer and coated paper, which hasalready been surface-treated.

The synthetic resin paper includes, for example, sheets made ofpolyester, polyvinyl chloride, polyethylene, polypropylene, polyethyleneterephthalate, polycarbonate and polyamide. The synthetic paperincludes, for example, those prepared by mixing a polyolefin resin oranother synthetic resin as a resin component with inorganic fillers,followed by extrusion molding of the mixture.

By using paper as the substrate, the sheet coated with a powdery coatingcomposition and image-receiving sheet for an ink-jet recording of theinvention can be produced at low cost.

The sheet coated with a powdery coating composition according to theinvention can be used as an image-receiving sheet for an ink-jetrecording comprising the above resin layer as a receiving layer for jetprinting ink, that is particularly suitable.

The powdery coating composition used in the invention contains a resin.This resin serves as a binding resin capable of integrating variouscomponents of the powdery coating composition into a powder, and alsoforms a resin layer as a receiving layer for jet printing-ink on asubstrate, as described above, and supports a colorant such as a dye orpigment constituting a letter or an image on recording of the letter orimage due to jet printing ink, thereby making it possible to record iton a receiving sheet.

According to the invention, the resin constituting the powdery coatingcomposition is not specifically limited, and there can be usedhydrophobic resin, hydrophilic resin including water-absorbing resin andwater-soluble resin, and a mixture thereof. The mixture of these resinsmay be a mixture of two or more kinds of resin particles, e.g. a mixtureof hydrophobic resin particles and water-absorbing resin particles orhydrophilic resin particles, or a composite prepared by melt-kneadingtwo or more kinds of resins, e.g. hydrophobic resin particles andwater-absorbing resin or water-soluble resin particles, followed bycooling, grinding and further classification of the mixture, asdescribed below.

The hydrophobic resin refers to those wherein the absorption amount ofdeionized water is 0.1 times or less, preferably 0.01 times or less, asmuch as its own weight. Specific examples thereof include styrenic resinsuch as saturated polyester resin, polyamide resin, (meth)acrylic resin,polyurethane resin, polyvinyl acetal resin, vinyl chloride resin, vinylacetate resin, vinyl chloride-vinyl acetate copolymer resin, vinylidenechloride resin, polystyrene resin, styrene-acrylic copolymer resin,styrene-butadiene copolymer resin, etc.; polyoelfinic resin such aspolyethylene resin, ethylene-propylene copolymer resin, ethylene-vinylacetate copolymer resin, polypropylene, etc.; and epoxy resin.

The above saturated polyester resin is a polymer obtained bycondensation polymerization of a dihydric carboxylic acid and a dihydricalcohol. The dihydric carboxylic acid is not specifically limited andincludes, for example, aliphatic dibasic acid such as malonic acid,succinic acid, glutaric acid, adipic acid, sebacic acid,hexahydrophthalic anhydride, etc.; and aromatic dibasic acid such asphthalic anhydride, phthalic acid, terephthalic acid, isophthalic acid,etc. If necessary, a polybasic acid (tribasic or more) may also be usedin combination. The polybasic acid includes, for example, trimelliticanhydride and pyromellitic anhydride.

Also the dihydric alcohol is not specifically limited and includes, forexample, ethylene glycol, propylene glycol, butylene glycol, hexanediol,neopentyl glycol, diethylene glycol, dipropylene glycol, hydrogenatedbisphenol A. If necessary, a polyhydric alcohol (trihydric or more) mayalso be used in combination. The polyhydric alcohol includes, forexample, glycerin, trimethylolpropane, diglycerin, pentaerythritol andsorbitol.

A commercially available product can be suitably used as the unsaturatedpolyester resin. The commercially available product includes, forexample, Bailon 103, 200, 290, 600 (manufactured by Toyobo Co.);KA-1038C (manufactured by Arakawa Chemical Co.); TP-220, 235 (NipponSynthetic Chemical Industry Co.); Diaculon ER-101, ER-501, FC-172,FC-344, FC-714 (manufactured by Mitsubishi Rayon Co.); and TafutonNE-382, 1110, 2155 (manufactured by Kao Corp.).

The styrene-acrylic copolymer resin is a copolymer of styrene and(meth)acrylate and specific examples of the (meth)acrylate includesethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate,butyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl acrylate,dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate.

As the styrene-acrylic copolymer resin, various commercially availableproducts can be suitably used. The commercially available productincludes, for example, Himer UNI-3000, TB-1800, TBH-1500 (manufacturedby Sanyo Chemical Industry Co.); and CPR-100, 600B, 200, 300, XPA4799,4800 (manufactured by Mitsui Chemical Co.).

It is preferred that the hydrophobic resin used in the invention has asoftening point within a range from 60 to 150° C., and preferably from70 to 120° C.

Also the water-absorbing resin is not specifically limited in a polymermaterial constituting it, but is preferably a chemically crosslinkedtype water-absorbing resin. The absorption amount of deionized water perunit weight of the resin is preferably within a range from 100 to 1000g/g, and particularly preferably from 300 to 1000 g/g.

The water-absorbing resin includes, for example, a substance prepared bypartially crosslinking polyacrylic acid with a sodium salt (e.g. Aquarik(registered trademark) CA manufactured by Nippon Catalyst Co. andSunfresh ST-500MPS, etc. manufactured by Sanyo Chemical Industry Co.)and starch-acrylic acid graft polymer partial sodium salt (e.g. SunfreshST-500MPS. ST-100, manufactured by Sanyo Chemical Industry Co.).

Other examples include crosslinked isobutylene-sodium maleate copolymer,crosslinked styrene-sodium maleate copolymer, grafted starch-sodiumpolyacrylate, saponified substance of grafted starch-polyacrylonitrile,grafted cellulose-sodium polyacrylate, and vinyl alcohol-sodium(meth)acrylate copolymer, etc. Such a chemically crosslinked typewater-absorbing resin can be commercially available.

The water-soluble resin includes, for example, polyvinyl alcohol,polyethylene oxide, polyethylene oxide polypropylene oxide,hydroxymethylcellulose, hydroxyethylcellulose, carboxymethylcellulose,and polyvinyl pyrrolidone.

It is preferred that the hydrophilic resin used in the invention has asoftening point within a range from 60 to 150° C. and preferably from 70to 120° C. When using the sheet coated with a powdery coatingcomposition of the invention, in the image-receiving sheet for anink-jet recording, the resin in the powdery coating composition is notspecifically limited as described above. For example, there can bepreferably used hydrophobic resins such as saturated polyester resin,styrene-acrylic copolymer resin, etc.; and mixtures of the hydrophobicresin and water-soluble resin such as polyvinyl alcohol, polyethyleneoxide, etc.

The powdery coating composition may contain additives such as colorantsor fillers, if necessary. The colorant is preferably a white colorantand, for example, titanium oxide is preferably used but is not limitedthereto. The colorant gives a requisite earth color to the substrate.The white colorant gives a white earth color to the substrate. Thecolorant is usually contained in the powdery coating composition in theamount within a range from 0.5 to 60% by weight, and preferably from 5to 50% by weight. As the filler, for example, silica and calciumcarbonate are used.

The powdery coating composition may further contain an anti-offsetagent, if necessary, so as not to cause offset when the powdery coatingcomposition is melted and fixed by heating after it is dry-coated on asubstrate. As the anti-offset agent, for example, various waxes having amelting point within a range from 50 to 150° C. are preferably used.Specific examples thereof include paraffin wax and polyolefin wax suchas polyethylene wax or polypropylene wax, fatty acid metal salt, fattyacid ester, higher fatty acid, and higher alcohol. Such an anti-offsetagent is normally used in the powdery coating composition in the amountwithin a range from 0.1 to 20% by weight, and preferably from 0.5 to 10%by weight.

As described above, the powdery coating composition containing thecolorant, filler and other additives, together with the resin, isobtained by mixing them, melt-kneading at a temperature within a rangeusually from about 100 to 200° C., preferably from about 130 to 180° C.,for several minutes, usually about 3 to 5 minutes, followed by cooling,grinding and further classification of the mixture. The powdery coatingcomposition has an average particle diameter within a range from 0.1 to30 μm, preferably from 1 to 25 μm, and most preferably from 5 to 20 μm.

As described above, the powdery coating composition contains thecolorant, filler and other additives, together with the resin. Accordingto the invention, the resin may be a composite prepared by integratingvarious resins into a powdery coating composition in various structuresor forms in the powdery coating composition.

That is, a most simple powdery coating composition is a compositionwhose resin component is made of a single resin (e.g. hydrophobic resin)having the same property. According to the invention, however, the resincomponent in the powdery coating composition may also be a compositemade of two or more kinds of resins having different properties.

For example, when a hydrophobic resin is melt-mixed with particles of awater-absorbing resin having an average particle diameter within a rangefrom 1 to 20 μm, preferably from 5 to 15 μm, and, if necessary, togetherwith the above-described additives, and the resulting mixture is groundinto particles having an average particle diameter of 5 to 20 μm, themixture is fractured exclusively at the interface between thehydrophobic resin and water-absorbing resin particles because theparticles of water-absorbing resin have a large average particlediameter. As a result, there can be obtained, as a powdery coatingcomposition, particles of hydrophobic resin composition containing theparticles of water-absorbing resin while exposing a portion of theparticles of the above water-absorbing resin on the surface of theparticles of the above hydrophobic resin.

Then, when the particles of the hydrophobic resin composition are mixedwith inorganic fine particles as described above, a powdery mixture canbe obtained. The proportion of the water-absorbing resin particles ispreferably from 5 to 50% by weight, and particularly preferable from 10to 30% by weight, based on the total amount of the hydrophobic resin andthe particles of water-absorbing resin.

Since the above-mentioned chemically crosslinked type water-absorbingresin is not melted by heating, even when the hydrophobic resin ismelted and mixed with the water-absorbing resin having an averageparticle diameter of larger than 20 μm and the mixture is ground, it isdifficult to uniformly disperse the water-absorbing resin in thehydrophobic resin. Therefore, the particles of the water-absorbing resinand the hydrophobic resin each exist as independent particles. In theinvention, however, when the particles of the water-absorbing resin andthe hydrophobic resin are melt-kneaded and ground, it is not necessaryto disperse all of the particles of water-absorbing resin used in thehydrophobic resin and a portion of the particles of the water-absorbingresin may exist as independent particles from the resulting particles ofhydrophobic resin composition. When the average particle diameter of theparticles of the water-absorbing resin is smaller than 1 μm, theparticles of the water-absorbing resin are uniformly dispersed in themixture and, therefore, the mixture is hardly fractured at theinterface.

According to such a powdery coating composition, since a portion of theparticles of the water-absorbing resin is exposed on the surface of theparticles of the hydrophobic resin, thus affording the hydrophilicity tothe particles of the hydrophobic resin, the absorbency and colordeveloping property of ink can be imparted to the resultingink-receiving layer.

According to the invention, when a hydrophobic resin and a water-solubleresin are optionally melt-kneaded with the additives and the resultingmixture is ground into particles having an average particle diameterwithin a range from 1 to 30 μm, preferably from 5 to 20 μm, thehydrophilic resin is dispersed in the mixture in the form of particlesbecause the hydrophilic resin has poor compatibility with thehydrophobic resin. As a result, the mixture is fractured exclusively atthe interface between the hydrophobic resin and the particles of thewater-soluble resin, thereby making it possible to obtain, as a powderycoating composition, particles of the hydrophobic resin compositioncontaining the above particles of the water-absorbing resin whileexposing a portion of the particles of the water-absorbing resin on thesurface of the particles of the hydrophobic resin.

Then, when the powdery coating composition is mixed with inorganic fineparticles as described above, the powdery mixture as describedhereinbefore can be obtained. The proportion of the particles of thewater-absorbing resin is preferably from 5 to 50% by weight, andparticularly preferable from 10 to 30% by weight, based on the totalamount of the hydrophobic resin and water-absorbing resin.

Such a particle of the powdery coating composition as described above isschematically shown in FIG. 1. That is, the powdery coating compositionis composed of particles 11 of water-soluble resin and a hydrophobicresin 12, and the particles of the water-soluble resin are dispersed inthe particles of the hydrophobic resin while exposing a portion of theparticles of the water-soluble resin on the surface of the particles ofthe hydrophobic resin. The powdery coating composition obtained bymelt-kneading a hydrophobic resin with particles of a water-absorbingresin, followed by grinding and further classification of the mixturealso has the same structure.

As described above, according to the powdery coating composition, aportion of the particles of the water-soluble resin is exposed on thesurface of the particles of the hydrophobic resin, thus affordinghydrophilicity to the particles of the hydrophobic resin. Thus, theabsorbency and color developing property of ink can be imparted to theink-receiving layer formed with the powdery coating composition.

Further according to the invention, when a hydrophobic resin and ahydrophilic inorganic fine particles having an average particle diameterof 1 to 5 μm are melt-kneaded and the resulting mixture is ground intoparticles having an average particle diameter of 5 to 20 μm, there canbe obtained particles of the hydrophilic resin composition containingthe hydrophilic inorganic fine particles while exposing a portion of thehydrophilic inorganic fine particles on the surface of the hydrophobicresin.

As described above, when the hydrophobic resin is melt-kneaded togetherwith the hydrophilic inorganic fine particles and cooled and theresulting mixture was ground into particles having an average particlediameter of 5 to 20 μm, the mixture was fractured exclusively at theinterface between the hydrophobic resin and inorganic fine particlesbecause the hydrophilic inorganic fine particles have a comparativelylarge average particle diameter, as the result, thereby making itpossible to obtain particles of hydrophobic resin composition wherein aportion of the inorganic fine particles having a large particle diameteris exposed on the surface of the particles of the hydrophobic resin.

According to such a powdery coating composition, a portion of theinorganic fine particles is exposed on the surface of the particles ofthe hydrophobic resin, thus affording hydrophilicity to the particles ofthe hydrophobic resin. Therefore, the ink-receiving layer formed withsuch particles of hydrophobic resin composition has absorbency and colordeveloping property of ink.

When the average particle diameter of the (first) hydrophobic inorganicfine particles, which are kneaded with the hydrophobic resin anddispersed in the mixture with the hydrophobic resin, is smaller than 1μm, the (first) inorganic fine particles are uniformly dispersed in themixture and the mixture is hardly fractured at the interface. On theother hand, when the average particle diameter of the first hydrophilicinorganic fine particles is larger than 5 μm, the first inorganic fineparticles exist together with the hydrophobic resin compositionparticles, as independent particles. Therefore, as described below, inthe case where a powdery mixture prepared by mixing this powdery coatingcomposition with the hydrophilic second inorganic fine particles havingan average particle diameter of 1 nm to 1 μm thereby to coat the surfaceof the particles of the hydrophobic resin composition with thehydrophilic second inorganic fine particles is dry-coated on thesubstrate and the powdery mixture is fixed by heating, good fixing islikely to be impaired.

The proportion of (first) inorganic fine particles is preferably withina range from 5 to 50% by weight, and particularly preferable from 10 to30% by weight, based on the total amount of the hydrophobic resin andthe (first) inorganic fine particles.

As hydrophilic (first) inorganic fine particles having an averageparticle diameter of 1 to 5 μm to be dispersed in the hydrophobic resin,for example, a commercially available product can be suitably used. Sucha commercially available product includes, for example, silica such asCarplex (manufactured by Shionogi Pharmaceutical Co.), Mizukasil(manufactured by Mizusawa Chemical Industry Co.), Fineseal X-37, 40, 70,80, etc. (manufactured by Tokuyama Co.); and calcium carbonate such asED-I, ED-III, ED-V (manufactured by Yonesho Sekkai Kogyo Co.), CalrightKT, etc. (manufactured by Shiraishi Calcium Co.).

Also regarding the powdery coating composition wherein the hydrophilicinorganic fine particles are dispersed in the particles of hydrophobicresin while exposing the surface of a portion of the inorganic fineparticles, the structure becomes apparent by displacing the particles ofwater-soluble resin with the hydrophilic inorganic fine particles inFIG. 1.

Furthermore, according to the invention, the powdery coating compositionmay be prepared by optionally mixing the hydrophobic resin with two ormore kinds selected from the water-absorbing resin, water-soluble resinand hydrophilic inorganic fine particles, followed by melt-kneading,grinding and further classification of the mixture. Particularly, apowdery coating composition obtained by mixing the hydrophobic resinwith the water-soluble resin and hydrophilic inorganic fine particles,followed by melt-kneading, grinding and further classification of themixture is a preferred example of the powdery coating composition usedin the present invention.

In the preparation of such a powdery coating composition, thewater-soluble resin and hydrophilic inorganic fine-particles are,respectively, used in the amount within a range from 5 to 50% by weight,and their total amount is preferably from 10 to 60% by weight.

According to the invention, when such a powdery coating composition ismixed with inorganic fine particles having an average particle diameterwithin a range from 1 nm to 1 μm to form a powdery mixture, as describedabove, and the resulting powdery mixture is dry-coated on the surface ofa substrate, melted by heating and then fixed, a porous and continuousresin layer comprising particles of the powdery coating composition anda substantially continuous film composed of the inorganic fine particlesand provided between the particles of powdery coating composition toform space at least in part therebetween can be formed on the substrate.

The thickness of the resin layer formed of the powdery coatingcomposition is usually within a range from 1 to 100 μm, preferably from2 to 80 μm, and particularly preferable from 5 to 50 μm.

According to the invention, the resin layer of the powdery coatingcomposition may be formed by dry-coating the powdery mixture directly ona substrate, melting the powdery mixture by heating and fixing it, butan under-coat made of a proper resin may also be optionally provided soas to enhance the adhesion between the resin layer and the substrate, orthe smoothness of the substrate. Such an undercoat may be provided bydry-coating a proper powdery coating or coating of the resin solution.

FIG. 2 shows schematically a section of one embodiment of a sheet coatedwith such a powdery coating composition according to the invention. On asubstrate 21 there is provided a porous and continuous resin layer 25comprising particles of a powdery coating composition 22 and asubstantially continuous film 24 composed of inorganic fine particles 23and forming space between the particles of the powdery coatingcomposition, while a portion of the inorganic fine particles 23 isexposed on the surface of the resin layer 25.

The resin layer having such a specific structure can be obtained bymixing the inorganic fine particles with the powdery coating compositionin a predetermined proportion to form a powdery mixture, dry-coating thepowdery mixture on a substrate, melting the powdery mixture by heatingand fixing it. The proportion of the inorganic fine powders is usuallywithin a range from 0.5 to 10% by weight, preferably from 1 to 9% byweight, and most preferably from 5 to 8% by weight, in the powderymixture composed of the powdery coating composition and inorganic finepowders. However, the proportion can be experimentally decided accordingto each average particle diameter of the powdery coating composition andinorganic fine particles used, most preferably.

In a case where the proportion of the inorganic fine particles is toosmall, when the above powdery mixture is melted by heating thereby tofix on the substrate, it is impossible to form a porous and continuousresin layer comprised of particles of the powdery coating compositionhaving a substantially continuous film of inorganic fine particlesprovided between the particles of the powdery coating composition toform space therebetween. Accordingly, the image obtained by ink-jetrecording has not sufficient density. On the other hand, when theproportion of the inorganic fine particles is too large, fixing of theresin layer formed on the substrate is poor and the resin layer isliable to be peeled off from the substrate when the substrate is folded.Furthermore, the proportion of the powdery coating composition comprisedof the resin is too small and there is a fear that the density of theimage formed on the resin layer as the ink-receiving layer becomesinsufficient.

When the average particle diameter of the inorganic fine particles issmaller than 1 nm, even if the inorganic fine particles are used in acomparatively large amount, a porous and continuous resin layer havingspace between the particles of the powdery coating composition cannot beproduced.

On the other hand, when the average particle diameter is larger than 1μm, it is difficult to fix a powdery mixture of the inorganic fineparticles and powdery coating composition on a substrate afterdry-coating it on the substrate and melting by heating. Accordingly, theresin layer formed is peeled off from the substrate thereby to causedefects in the resulting coated sheet. Therefore, a high quality imagerecording cannot be obtained even if such a sheet coated with a powderycoating is used in an image-receiving sheet for an ink-jet recording.

According to the invention, hydrophilic inorganic fine particles arepreferred as the above-mentioned inorganic fine particles. Among them,fine particles of hydrophilic inorganic oxide and inorganic carbonateare particularly preferred. If necessary, hydrophilic inorganic fineparticles may be used in combination with hydrophobic inorganic fineparticles according to the purpose and required characteristics of theresulting sheet coated with a powdery coating.

When using the sheet coated with a powdery coating composition of theinvention, as an image-receiving sheet for an ink-jet recording,hydrophilic inorganic fine-particles can be optionally used incombination with hydrophobic inorganic fine-particles so as to controlthe absorbency of water based jet printing ink of the ink-receivinglayer.

These inorganic fine particles are commercially available easily. Thecommercially available product of the hydrophilic inorganic fineparticles includes inorganic oxide fine particles, for example, Aerosil®50, 90G, 130, 200, 200V, 200CF, 200FAD, 300, 300CF, 380, OX50, TT600,MOX80, MOX170, COK 84 (anhydrous silica, manufactured by Nippon AerosilCo.); Aluminum Oxide C, Titanium Dioxide P25 (manufactured by NipponAerosil Co.); Caplex® FPS-2, FPS-3, FPS-4, FPS-5, FPS-101, CS-5, CS-7,BS-304F, BS-304N (manufactured by Shionogi & Co.); and inorganic oxidefine particles S13, V15, N20, T30, T40 (anhydrous silica, manufacturedby Clariant Japan Co.). Calite KT as calcium carbonate manufactured byShiraishi Industry Co. can also be used as the hydrophilic inorganicfine-particles.

On the other hand, the commercially available product of the hydrophobicinorganic fine particles includes, for example, Aerosil® R972, R972V,R972CF, R974, R202, R805, R812S (anhydrous silica, manufactured byNippon Aerosil Co.); T805, RX200, RY200 (titanium dioxide, manufacturedby Nippon Aerosil Co.); and H15, H20, H30, H2000, H2000/4, H3004,H2015EP, H2050EP (anhydrous silica, manufactured by Clariant Japan Co.).

Such a sheet coated with a powdery coating composition according to theinvention has a porous and continuous resin layer comprising particlesof powdery coating composition and a substantially continuous filmcomprising inorganic fine particles interposed between the particles ofthe powdery coating composition thereby to form space at least in parttherebetween, as described hereinbefore.

As a result, as described above, the inorganic fine particles areexposed on the surface of the resin layer in the form of a film, whilethe particles of the powdery coating composition are made to contactwith each other while interposing the inorganic fine particlestherebetween to form space (composed of the inorganic fine particles) atleast in part usually of about 1 to 200 nm therebetween. However, in aportion, the particles of powdery coating composition may not be made tocontact with each other and pores or voids may be present between theparticles.

As described above, since the sheet coated with a powdery coatingcomposition of the invention has a porous and continuous resin layercomprised of particles of the powdery coating composition and inorganicfine particles dispersed and interposed between the particles of powderycoating composition to form at least in part space therebetween, thesheet can be suitably used as an image-receiving sheet for an ink-jetrecording.

That is, when water based jet printing ink is adhered to such animage-receiving sheet, water in ink is rapidly permeated through theimage-receiving layer along the film composed of the inorganic fineparticles interposed between the particles of the powdery coatingcomposition and, at the same time, the resin layer containing thehydrophilic inorganic fine particles and the layer of the hydrophilicinorganic fine particles on the resin layer adsorb and scavenge thecolorant made of a dye or pigment in ink. Therefore, high-qualityink-jet recording having excellent absorbency and color developingproperty can be obtained.

The resin layer comprising the particles of the powdery coatingcomposition is formed on a substrate by dry-coating a powdery mixturecomposed of the powdery-coating composition and inorganic fine particleson the substrate, heating to melt the powdery coating composition, andfixing the powdery coating composition together with the inorganic fineparticles on the substrate.

The powdery mixture can be dry-coated on a substrate, for example, byelectrophotographic systems such as electrostatic spray method,electrostatic coating such as electrostatic dipping method, flame spraymethod, spray coating method, dispersion method, powder coating such aspowder melt lamination method, powder scatter method, cascade method,magnetic brush developing method, powder cloud method, open chambermethod, fur developing method, print developing method, and a developingmethod due to electrostatic induction.

Among these dry coating methods, an electrostatic spray method can bepreferably used in the invention. This electrostatic spray method is akind of powder coating, but is specified by transporting a powderymixture of fine-particles to a tip of a spray gun by air, applying anegative high potential (e.g. −50 to −90 kV) to a needle electrodeincorporated into the tip of the spray gun thereby to negatively chargethe powder mixture, closely placing an electrode grounded on the backsurface of the substrate, and transporting the negatively chargedpowdery mixture to the substrate due to an electric field, which ispresent between the spray gun and ground electrode, thereby to adherethe powdery mixture on the substrate electrostatically.

FIG. 3 shows preferred embodiment of the method using such anelectrostatic spray method according to the invention. That is, acontinuous long substrate (e.g. ordinary paper) 32 unwound from a roller31 is transported into a booth 34 by a carrier belt 33. In the booth,the powdery mixture is dry-coated by the electrostatic spray method,melted by heating by a fixing roller 35, fixed and then wound orappropriately cut, as described below. The carrier belt 33 has anelectrode 36 ground on the backside (i.e. positive electrode) along thesubstrate to be carried by the carrier belt. The powdery mixture iscarried to a spray gun 38 from a storage tank 37 by compressed air,while a negative high voltage is applied to a needle electrode (notshown) incorporated into the tip of the spray gun by a d.c. power sourceand the powdery mixture is negatively charged. Thus, the powdery mixtureis transported to the substrate by electric field, which is presentbetween the spray gun and the above electrode along the substrate on thecarrier belt, and then adhered to the substrate electrostatically. Insuch a way, the substrate dry-coated with the powdery mixture istransported to the fixing roller 35, where the powdery mixture is meltedby heating and then fixed on the substrate to form a resin layer, thusobtaining a sheet 40 coated with a powdery coating according to theinvention.

According to the invention, there is provided a further image-receivingsheet for an ink-jet recording, wherein an ink-receiving layer has atwo-layer structure. This image-receiving sheet for an ink-jet recordingcomprises a resin layer having a thickness of 1 to 100 μm on a substrateand a surface layer formed on the resin layer. The resin layer iscomposed of particles of powdery coating composition having an averageparticle diameter of 0.1 to 30 μm and containing a resin and a colorant.The surface layer is composed of inorganic fine particles having anaverage particle diameter of 1 to 50 nm. The resin layer preferably hasat least in part space between the particles of powdery coatingcomposition.

Such an image-receiving sheet for an ink-jet recording can be obtainedaccording to the invention by a method comprising the step ofdry-coating particles of a powdery coating composition having an averageparticle diameter of 0.1 to 30 μm and containing a resin and a colorant,on a substrate, to form a resin layer, the step of forming a surfacelayer composed of inorganic fine particles having an average particlediameter of 1 to 50 nm on the resin layer, the step of fixing the resinlayer on the substrate, and fixing the surface layer composed of theinorganic fine particles on the resin layer.

More specifically, particles of the powdery coating composition havingan average particle diameter of 0.1 to 30 μm and containing a resin anda colorant are dry-coated on a substrate to form a resin layer and theninorganic fine particles having an average particle diameter of 1 to 50nm are dry-coated on the resin layer to form a surface layer on theresin layer. Then, the laminated sheet thus obtained is heated underpressurizing thereby to fix the resin layer on the substrate and to fixthe surface layer of the inorganic fine particles on the resin layer.When the resin layer is formed, the powdery coating composition isheated to a temperature lower than that at which the powdery coatingcomposition is completely melted to form continuous coated film, therebyto incompletely, i.e. partially melt the powdery coating composition.Thus, the powdery coating composition is partially adhered to each otherto form a resin layer having space at least in part therebetween.

According to the invention, however, it is preferred that the powderycoating composition is mixed with a predetermined proportion, usually0.5 to 10% by weight, of a first inorganic fine particles to form apowdery mixture, dry-coating the powdery mixture on a substrate to form,as an ink-receiving layer, a porous and continuous resin layer composedof the particles of the powdery coating composition and inorganic fineparticles dispersed between the particles of the powdery coatingcomposition thereby to form space at least in part therebetween, asdescribed above. Then, second inorganic fine particles having an averageparticle diameter of 1 to 50 nm are preferably dry-coated on the resinlayer to form a surface layer, thus obtaining an image-receiving sheetfor an ink-jet recording.

The image-receiving sheet for an ink-jet recording as a particularlypreferred one embodiment of the invention comprises a substrate and aporous and continuous resin layer having a thickness of 1 to 100 μmprovided on the substrate, the resin layer comprising particles ofpowdery coating composition having an average particle diameter of 0.1to 30 μm and containing a resin and a colorant, and the first inorganicfine particles having an average particle diameter of 1 nm to 1 μmdispersed between the particles of powdery coating composition to formspace at least in part therebetween, the sheet further comprising asurface layer composed of the second inorganic fine particles having anaverage particle diameter of 1 to 50 nm on the resin layer.

When the average particle diameter of the second inorganic fineparticles is larger than 50 nm, in a case where an ink-jet recording ofan image-receiving sheet having such a layer of inorganic fine particlesis performed, the resulting image sometimes lacks accuracy and animage-receiving sheet for an ink-jet recording capable of affording ahigh quality recorded image cannot be obtained sometimes. The secondinorganic fine particles may have an average particle diameter ofsmaller than 1 nm, but preferably have an average particle diameter ofnot less than 1 nm in view of availability.

Such an image-receiving sheet for an ink-jet recording can be obtainedby a method comprising the step of dry-coating a powdery mixtureprepared by mixing a powdery coating composition having an averageparticle diameter of 0.1 to 30 μm and containing a resin and a colorant,with the first inorganic fine particles having an average particlediameter of 1 nm to 1 μm on a substrate to form a powdery mixture layer;the step of dry-coating the second inorganic fine particles on thepowdery mixture layer to form a surface layer; the step of melting thepowdery mixture layer by heating and fixing to form a resin layer; andthe step of fixing the surface layer made of the second inorganic fineparticles on the resin layer.

Now a preferred embodiment of the production of the image-receivingsheet for an ink-jet recording according to the invention will bedescribed.

For the production of the image-receiving sheet for an ink-jet recordingof the invention, first, a powdery coating composition having an averageparticle diameter of 0.1 to 30 μm, preferably 1 to 25 μm, is mixed withthe first inorganic fine particles having an average particle diameterof 1 nm to 1 μm to form a powdery mixture and, the powdery mixture isthen dry-coated on a substrate to form a powdery mixture layer. In theinvention, an intermediate product wherein the powdery mixture layer isformed on the substrate is referred to as a precursor sheet. Then, thesecond inorganic fine-particles having an average particle diameter of 1to 50 nm, preferably from 5 to 30 nm, are dry-coated on the powderymixture layer of the precursor sheet to form a surface layer. In theinvention, an intermediate product wherein the surface layer made ofinorganic fine particles is formed on the precursor sheet is referred toas a laminated sheet.

Then, the laminated sheet thus obtained is heated under pressurizingthereby to fix a porous and continuous resin layer comprised of theparticles of the powdery coating composition having the first inorganicfine particles dispersed between the particles of the powdery coating toform at least in part space therebetween on the substrate, and pressinga surface layer composed of the second inorganic fine particles on theresin layer thereby to fix it thereon.

However, fixing of the powdery mixture layer and fixing of the surfacelayer made of the second inorganic fine particles can be conductedseparately. That is, the powdery mixture may be dry-coated on thesubstrate to form a powdery mixture layer, thus obtaining a precursorsheet, which may be heated under pressure thereby to melt the powderycoating composition and to fix on the substrate to form a resin layer onthe substrate. Then, the second inorganic fine particles are dry-coatedon the resin layer and heated again under pressure thereby to fix theinorganic fine particles on the resin layer to form a surface layer.

The surface layer comprised of the second inorganic fine particles maycontain a binder and other additives. Particularly, the surface layercan be fixed to the resin layer as the ink-receiving layer, morestrongly, when the surface layer contains a binder. The binder is notspecifically limited, but various resins such as a resin for forming thepowdery coating composition can be used.

Among the various resins mentioned hereinbefore, when the hydrophobicresin, water-soluble resin or a mixture of these is used as a powder tomix with the second inorganic fine particles and the resulting mixtureis dry-coated on a resin layer as the ink-receiving layer and thenheated under pressure, the second inorganic fine particles are pressedon the resin layer while binding each other by the binder, therebybonding the second inorganic fine particles strongly on the resin layer.The binder is usually used in an amount within a range from 1 to 200parts by weight, and preferably from 5 to 100 parts by weight, based on100 parts by weight of the second inorganic fine particles.

However, the surface layer composed of the second inorganic fineparticles may be formed optionally by wet-coating, and not dry-coatingdescribed above. That is, a surface layer composed of the secondinorganic fine particles can also be formed on the resin layer bydispersing the second inorganic fine particles in a medium, preferablyaqueous medium such as water, adding a binder to prepare a coatingsolution, coating the coating solution on a resin layer as theimage-receiving layer, and drying the coating solution. When the powderycoating composition forming the resin layer is not dissolved or swollen,a binder may be formed by using a non-aqueous (or an organic) solvent.

In a case where a surface layer made of the second inorganic fineparticles is formed on a resin layer as the ink-receiving layer bywet-coating, various resins can be used as a latex, includingwater-soluble resin. As for the latex, for example, there can bepreferably used latex of hydrophobic resin, such as (meth)acrylic resin,styrene-acrylic copolymer resin, ethylene-vinyl acetate copolymer resin,polyvinyl acetal resin, epoxy resin, styrene-butadiene copolymer resin,polyethylene resin and polypropylene resin.

The image-receiving sheet for an ink-jet recording thus obtained has theresin layer usually of a thickness within a range from 1 to 100 μm,preferably from 2 to 80 μm, and particularly preferable from 5 to 50 μm.The surface layer composed of the second inorganic fine particlesusually has a thickness of 10 nm to 3 μm, and preferably from 20 nm to 1μm.

FIG. 4 schematically shows a section of one preferred embodiment of theimage-receiving sheet for an ink-jet recording according to theinvention. On a substrate 41, each of the particles of the powderycoating composition 42 forms a porous and continuous resin layer 45while a substantially continuous film 44 composed of the first inorganicfine particles 43 is interposed between the particles of the powderycoating composition to form space therebetween, and a portion of thefirst inorganic fine particles 43 is exposed on the surface of the resinlayer 45. A surface layer 47 comprised of the second inorganic fineparticles 46 is further formed on the resin layer 45.

The second inorganic fine particles are preferably hydrophilic, and fineparticles of hydrophilic inorganic oxide or carbonate are particularlypreferred. However, hydrophilic inorganic fine particles may beoptionally used in combination with hydrophobic inorganic fineparticles.

The second inorganic fine particles include, for example, the same firstinorganic fine particles as those described above. However, the firstinorganic fine particles and second inorganic fine particles may be thesame or different.

As described above, the image-receiving sheet for an ink-jet recordingaccording to the invention comprises a substrate and a porous andcontinuous resin layer as a first layer on the substrate, the resinlayer comprising particles of powdery coating composition and asubstantially continuous film comprised of the first inorganic fineparticles interposed or dispersed between the particles of powderycoating composition to form space at least in part therebetween, and thesheet further comprising a surface layer comprised of the secondinorganic fine particles as a second layer on the resin layer.Therefore, when water based jet printing ink is adhered to theimage-receiving sheet, a dye or pigment in ink is rapidly adsorbed andscavenged by the surface layer of the hydrophilic second inorganic fineparticles constituting the surface layer of the image-receiving layer,thereby making it possible to form a high density image.

Moreover, the image-receiving sheet of the invention has a porous andcontinuous resin layer comprising particles of powdery coatingcomposition and a substantially continuous film composed of the firstinorganic fine particles dispersed between the particles of the powderycoating composition to form space at least in part therebetween underthe surface layer composed of the second inorganic fine particles. Thus,water in jet printing ink penetrates through the surface layer composedof the second inorganic fine particles and is rapidly adsorbed andscavenged along the film composed of inorganic fine particles betweenthe particles of the powdery coating composition, and then retained inthe image-receiving layer.

Thus, water does not reach the substrate, that is, the substrate is notwetted even if the substrate is paper. On the other hand, water isadsorbed and scavenged by the first inorganic fine particles even if thesubstrate is a synthetic resin film and, therefore, the image is notsmudged.

The second inorganic fine particles are dry-coated on the resin layer byvarious methods, like the case where the powdery mixture is dry-coatedon the substrate, and an electrostatic spray method can be used,particularly preferable.

Such a two-layer structure image-receiving sheet for ink-jet recordingcan be continuously produced using an electrostatic spray method, forexample, by forming a resin layer comprised of a powdery mixture on asubstrate, transporting into a second booth, dry-coating the secondinorganic fine particles on the resin layer by using a second spray gun,pressing the second inorganic fine-particles by heating on the resinlayer, and fixing, as described with reference to FIG. 3.

EXAMPLES

The following examples further illustrate the invention in detail butare not to be construed to limit the scope thereof. In the followingexamples, parts and percentages are by weight unless otherwise stated.

Example 1 Preparation of Powdery Coating Composition and Powdery Mixture

40 parts of a saturated polyester resin (FC-344, manufactured byMitsubishi Rayon Co.), 30 parts of a styrene-acrylic copolymer resin(CPR-200, manufactured by Mitsui Chemical Co.) and 25 parts of a whitecolorant (titanium oxide (Taipake A220), manufactured by Ishihara SangyoCo.) were melt-kneaded in a double-screw melt-kneader at 150-160° C. for4 minutes. After cooling, the resulting mixture was ground andclassified to obtain a white powdery coating composition having anaverage particle diameter of 11.0 μm. 95 parts of the white powderycoating composition were mixed with 5 parts of a hydrophilic anhydroussilica (Aerosil 200, average particle diameter: 12 nm, manufactured byNippon Aerosil Co.) to obtain a white powdery mixture (proportion ofanhydrous silica: 5%) for dry coating by an electrostatic spray method.

Production of Image-receiving Sheet for an Ink-jet Recording)

Using a commercially available electrostatic spray device, the abovewhite powdery mixture was adhered on the entire surface of acommercially available ordinary paper, followed by melting by heatingand further fixing to form an image-receiving layer having a thicknessof 20 μm, thus obtaining a sheet coated with a powdery coatingcomposition.

Only the resin layer of the thus obtained sheet was embedded into anepoxy resin and then frozen to prepare a thin film having a thickness ofabout 1000 Å. The thin film was dyed with ruthenium oxide, reinforcedwith carbon and then observed by a transmission electron microscope. Atransmission electron micrograph of a section of the resin layer of thesheet is shown in FIG. 5. In the electron micrograph, the white portionshows an epoxy resin and the left side portion shows a resin layer. Theregion A is composed of a polyester resin, the region B astyrene-acrylic copolymer resin, the particles C are composed oftitanium dioxide, and the region D is composed of fine particles ofsilica which is substantially continuous in the form of a film anddispersed between the respective particles of powdery coatingcomposition, thereby to form space between the particles of powderycoating composition.

Ink-jet Recording

Using a commercially available ink-jet printer (manufactured by EpsonCo.), an ink-jet recording of an image-receiving sheet was performed. Asa result, a high quality recorded image could be obtained rapidly.

Production of Image-receiving Sheets Having Different Amounts of Silicaand Evaluation of Performances

In the same manner as described above, 40 parts of a saturated polyesterresin, 30 parts of a styrene-acrylic copolymer resin, 0.3, 1, 3, 8 or 12parts of anhydrous silica, and a white colorant were used so that thetotal amount of these became 100 parts to prepare a white powderymixture for dry coating, which contains 0.3, 1, 3, 8 or 12% of anhydroussilica. Using the resulting white powdery mixture, an image-receivingsheet for an ink-jet recording was produced and ink-jet recording of theimage-receiving sheet was performed.

The case where the image-receiving layer was not changed even when eachimage-receiving sheet for an ink-jet recording thus obtained was bentwas rated with an excellent fixing (A) of the image-receiving layer tothe substrate, while the case where powders were peeled from theimage-receiving sheet when the image-receiving sheet was bent was ratedwith poor fixing (B).

With respect to each image-receiving sheet, the density of the resultingimage due to an ink-jet recording was measured by using a densitometer(PDA-60, manufactured by Konica Co.). As a result, the case wheredensity of yellow and that of magenta are not less than 0.9 and densityof cyan is not less than 0.5 was rated excellent image density (A),while the case where the density of yellow and that of magenta aresmaller than 0.9 or the density of cyan is smaller than 0.5 was ratedpoor image density (B).

Furthermore, the permeability of ink to the image-receiving layer andthe fixing of ink to the image-receiving layer in an ink-jet recordingwere examined in the following procedure. With respect to thepermeability of ink, the case where jet printing ink permeated throughthe image-receiving layer to form a clear image was rated excellentpermeability (A), while the case where ink did not permeate through theimage-receiving layer and the image-receiving layer repelled ink wasrated poor permeability (B). The above results are shown in Table 1.

TABLE 1 Amount of Silica (% by weight)*⁾ 0.3 1.0 3.0 5.0 8.0 12.0 ImageDensity A A A A A A Permeability B A A A A A Fixing A A A A A B*⁾Proportion of silica to the total of powdery coating composition andsilica (powdery mixture)

Example 2 Preparation of Powdery Coating Composition and Powdery Mixture

70 parts of a styrene-acrylic copolymer resin (CPR-200, manufactured byMitsui Chemical Co.) and 22 parts of a white colorant (titanium oxide(Taipake R550), manufactured by Ishihara Sangyo Co.) were melt-kneadedin a double-screw melt-kneader at 150-160° C. for 4 minutes. Aftercooling, the resulting mixture was ground and classified to obtain awhite powdery coating composition having an average particle diameter of11.0 μm. 92 parts of the white powdery coating composition was mixedwith 8 parts of a hydrophilic anhydrous silica (Aerosil 200CF, averageparticle diameter: 12 nm, manufactured by Nippon Aerosil Co.) to obtaina white powdery mixture (proportion of anhydrous silica: 8%) for drycoating by an electrostatic spray method.

In the same manner as described in Example 1, 70 parts of astyrene-acrylic copolymer resin, 3 or 5 parts of anhydrous silica and awhite colorant were used so that the total weight of these became 100parts to prepare a white powdery mixture for dry coating, which contains3 or 5% of anhydrous silica.

Production of Image-receiving Sheet for an Ink-jet Recording

Using a commercially available electrostatic spray device, the abovewhite powdery mixture was adhered on the entire surface of acommercially available ordinary paper, followed by melting by heatingand further fixing to form an image-receiving layer having a thicknessof 20 μm, thus obtaining an image-receiving sheet for an ink-jetrecording.

Ink-jet Recording

Using a commercially available ink-jet printer (manufactured by EpsonCo.), an ink-jet recording of each image-receiving sheet thus obtainedwas performed. As a result, a high quality recorded image could beobtained rapidly in the case of any image-receiving sheet.

In the same manner as in Example 1, the fixing of the image-receivinglayer to the substrate, image density due to an ink-jet recording, andpermeability of ink to the image-receiving layer in an ink-jet recordingwere evaluated. As a result, any image-receiving sheet was rated ‘A’.

Example 3 Preparation of Powdery Coating Composition and Powdery Mixture

70 parts of a styrene-acrylic copolymer resin (CPR-200, manufactured byMitsui Chemical Co.) and 22 parts of a white colorant (titanium oxide(Taipake R550), manufactured by Ishihara Sangyo Co.) were melt-kneadedin a double-screw melt-kneader at 150-160° C. for 4 minutes. Aftercooling, the resulting mixture was ground and classified to obtain awhite powdery coating composition having an average particle diameter of11.0 μm. 92 parts of the white powdery coating composition was mixedwith 8 parts of hydrophilic aluminum oxide (Aluminum Oxide C, averageparticle diameter: 13 nm, manufactured by Nippon Aerosil Co.) to obtaina white powdery mixture (proportion of aluminum oxide: 8%) for drycoating by an electrostatic spray method.

In the same manner as in Example 1, 70 parts of a styrene-acryliccopolymer resin, 3 or 5 parts of aluminum oxide and a white colorantwere used so that the total weight of these became 100 parts to preparea white powdery mixture for dry coating, which contains 3 or 5% byweight of aluminum oxide.

Production of Image-receiving Sheet for an Ink-jet Recording

Using a commercially available electrostatic spray device, the abovewhite powdery mixture was adhered on the entire surface of acommercially available ordinary paper, followed by melting by heatingand further fixing to form an image-receiving layer having a thicknessof 20 μm, thus obtaining an image-receiving sheet for an ink-jetrecording.

Ink-jet Recording

Using a commercially available ink-jet printer (manufactured by EpsonCo.), an ink-jet recording of each image-receiving sheet thus obtainedwas performed. As a result, a high quality recorded image could beobtained rapidly in the case of any image-receiving sheet.

In the same manner as in Example 1, the fixing of the image-receivinglayer to the substrate, image density due to ink-jet recording, andpermeability of ink to the image-receiving layer in an ink-jet recordingwere evaluated. As a result, any image-receiving sheet was rated ‘A’.

Example 4 Preparation of Powdery Coating Composition and Powdery Mixture

70 Parts of a styrene-acrylic copolymer resin (CPR-200, manufactured byMitsui Chemical Co.) and 22 parts of a white colorant (titanium oxide(Taipake R550), manufactured by Ishihara Sangyo Co.) were melt-kneadedin a double-screw melt-kneader at 150-160° C. for 4 minutes. Aftercooling, the resulting mixture was ground and classified to obtain awhite powdery coating composition having an average particle diameter of11.0 μm. 92 parts of this white powdery coating composition was mixedwith 8 parts of a hydrophilic anhydrous titanium dioxide (TitaniumDioxide P25, average particle diameter: 21 nm, manufactured by NipponAerosil Co.) to obtain a white powdery mixture (proportion of titaniumdioxide: 8%) for dry coating by an electrostatic spray method.

In the same manner as in Example 1, 70 parts of a styrene-acryliccopolymer resin, 3 or 5 parts of titanium dioxide (P25) and a whitecolorant were used so that the total weight of these became 100 parts toprepare a white powdery mixture for dry coating, which contains 3 or 5%by weight of titanium dioxide (P25).

Production of Image-receiving Sheet for an Ink-jet Recording

Using a commercially available electrostatic spray device, the abovewhite powdery mixture was adhered on the entire surface of acommercially available ordinary paper, followed by melting by heatingand further fixing to form an image-receiving layer having a thicknessof 20 μm.

Ink-jet Recording

Using a commercially available ink-jet printer (manufactured by EpsonCo.), an ink-jet recording of each image-receiving sheet thus obtainedwas performed. As a result, a high quality recorded image could beobtained rapidly in the case of any image-receiving sheet.

In the same manner as in Example 1, the fixing of the image-receivinglayer to the substrate, image density due to ink-jet recording, andpermeability of ink to the image-receiving layer in an ink-jet recordingwere evaluated. As a result, any image-receiving sheet was rated ‘A’.

Comparative Example 1

The white powdery coating composition prepared in Example 1 wasdissolved in methyl ethyl ketone to prepare an oil base coatingcomposition. The composition was coated on a ordinary paper using a barcoater and then dried to obtain an image-receiving sheet for an ink-jetrecording.

Using the same commercially available ink-jet printer as in Example 1,an ink-jet recording of the image-receiving sheet was performed.However, the image-receiving layer repelled jet printing ink and animage could not be recorded.

Example 5 Preparation of Powdery Coating Composition and Powdery Mixture

50 parts of a saturated polyester resin (FC-714, manufactured byMitsubishi Rayon Co.) and 45 parts of a white colorant (titanium oxide(Taipake A220), manufactured by Ishihara Sangyo Co.) were melt-kneadedin a double-screw melt-kneader at 150-160° C. for 4 minutes. Aftercooling, the resulting mixture was ground and classified to obtain awhite powdery coating composition having an average particle diameter of11.0 μm. 95 parts of this white powdery coating composition was mixedwith 5 parts of a hydrophilic anhydrous silica (Aerosil 200, averageparticle diameter: 12 nm, manufactured by Nippon Aerosil Co.) to obtaina white powdery mixture (proportion of anhydrous silica: 5%) for drycoating by an electrostatic spray method.

Production of Image-receiving Sheet for an Ink-jet Recording

Using a commercially available electrostatic spray device, the abovewhite powdery mixture was adhered on the entire surface of acommercially available ordinary paper to form a resin layer. Using thesame device, a hydrophilic anhydrous silica (Aerosil 200, averageparticle diameter: 12 nm, manufactured by Nippon Aerosil Co.) as thesecond inorganic fine particles was adhered on the above resin layer.Then, the laminated sheet thus obtained was heated under pressure,thereby to fix the resin layer on the ordinary paper. At the same time,the second inorganic fine-particles were fixed on the resin layer bypressing, thus obtaining an image-receiving sheet for an ink-jetrecording having a surface layer composed of the second inorganic fineparticles having a thickness of about 1 μm on an image-receiving layerhaving a thickness of 20 μm.

Ink-jet Recording

Using a commercially available ink-jet printer (manufactured by EpsonCo.), an ink-jet recording of each image-receiving sheet thus obtainedwas performed. As a result, an accurate recorded image having highdensity could be obtained rapidly.

Comparative Example 2

In the same manner as in Example 5, except that particles of polymethylmethacrylate having an average particle diameter of 150 nm were used asthe second inorganic fine particles, an image-receiving sheet for anink-jet recording having a surface layer composed of particles ofpolymethyl methacrylate having a thickness of about 3 μm on animage-receiving layer having a thickness of 20 μm was obtained.

In the same manner as in Example 5, an ink-jet recording of theimage-receiving sheet for an ink-jet recording was performed. However,the image-receiving sheet repelled ink and an image could not berecorded.

Comparative Example 3

In the same manner as in Example 5, except that a hydrophilic silicahaving a particle diameter of 5 to 50 μm was used as the secondinorganic fine particles, an image-receiving sheet for an ink-jetrecording having a surface layer composed of the above silica having athickness of about 50 μm on an image-receiving layer having a thicknessof 20 μm was obtained.

In the same manner as in Example 5, an ink-jet recording of theimage-receiving sheet for an ink-jet recording was performed. As aresult, ink was not absorbed into particles of the hydrophilic silica ofthe surface layer of the image-receiving sheet, but permeated through aspace between the silica particles. Therefore, ink dots were not formedon the outermost surface of the image-receiving sheet and only an imagehaving low density was formed. In an ink-jet recording, an image havinghigh density cannot be formed until ink dots are not formed on theoutermost surface of the image-receiving sheet.

Example 6 Preparation of Powdery Coating Composition

80 parts of a styrene-acrylic copolymer resin (Himer Uni-3000, softeningpoint: 98 C, manufactured by Sanyo Chemical Industry Co.) and 20 partsof fine particles of hydrophilic silica (Mizukasil P-527, averageparticle diameter: 1.6 μm, manufactured by Mizusawa Chemical IndustryCo.) were melt-kneaded. After cooling, the resulting mixture was groundand classified to obtain a hydrophobic resin powdery coating compositionhaving an average particle diameter of 11.0 μm. 100 parts of thishydrophobic resin powdery coating composition and 5 parts offine-particles of hydrophilic silica (average particle diameter: 12 nm,manufactured by Nippon Aerosil Co.) were mixed by stirring to obtain apowdery mixture.

Production of Image-receiving Sheet for an Ink-jet Recording

Using a commercially available electrostatic spray device, the abovepowdery mixture was sprayed on the entire surface of a commerciallyavailable ordinary paper and the powdery mixture was heated to about 80to 100° C. under pressure, thereby to fix the powdery mixture to theordinary paper. At the same time, particles of powdery coatingcomposition were fused to each other, partially, to form a resin layerhaving a thickness of 20 μm, having space between the particles, as animage-receiving layer Thus, an image-receiving sheet for an ink-jetrecording was obtained.

Ink-jet Recording Characteristics

Using a commercially available ink-jet printer (PM-750C, manufactured byEpson Co.), an ink-jet recording of the image-receiving sheet for anink-jet recording was performed, and then the absorbency and colordeveloping property of ink was examined. The absorbency of ink wasexamined as follows. A color chart defined by the Japanese StandardsSociety was ink-jet recorded on a recording paper and, immediately afterrecording, the image was touched by fingertip. The case where ink wasnot adhered to the fingertip was rated “good”, while the case where inkwas partially adhered to the fingertip was rated “poor”. The colordeveloping property of ink was examined by measuring the density of themost dense portion using a Macbeth densitometer (model RD-914). Theresults are shown in Table 2.

Example 7

In the same manner as in Example 6, except that 80 parts of astyrene-acrylic copolymer resin and 20 parts of fine particles ofhydrophilic calcium carbonate (ED-V, average particle diameter: 5.0 μm,manufactured by Yonesho Sekkai Kogyo Co.) were melt-kneaded to prepare apowdery mixture and an image-receiving sheet for an ink-jet recordingwas prepared by using the powdery mixture. In the same manner as inExample 6, the absorbency and color developing property of ink wasexamined. The results are shown in Table 2.

Comparative Example 4

In the same manner as in Example 6, except that 90 parts of astyrene-acrylic copolymer resin and 10 parts of fine particles ofhydrophilic silica (Aerosil 50, average primary particle diameter: 30nm, manufactured by Nippon Aerosil Co.) were melt-kneaded to prepare apowdery mixture and an image-receiving sheet for an ink-jet recordingwas prepared by using the powdery mixture. In the same manner as inExample 6, the absorbency and color developing property of ink wasexamined. The results are shown in Table 2.

Example 8

93 parts of a styrene-acrylic copolymer resin (Himer Uni-3000, softeningpoint: 98° C., manufactured by Sanyo Chemical Industry Co.) and 7 partsof a water-absorbing resin (prepared by partially crosslinkingpolyacrylic acid with a sodium salt, average particle diameter: 6.0 μm)were melt-kneaded. After cooling, the resulting mixture was ground andclassified to obtain a hydrophobic resin powdery coating compositionhaving an average particle diameter of 11.0 μm. Then, 100 parts of thehydrophobic resin powdery coating composition and 5 parts offine-particles of hydrophilic silica (Aerosil 200, average particlediameter: 12 nm, manufactured by Nippon Aerosil Co.) were mixed bystirring to prepare a powdery mixture. Then, an image-receiving sheetfor an ink-jet recording was prepared by using the powdery mixture. Inthe same manner as in Example 6, the absorbency and color developingproperty of ink was examined. The results are shown in Table 2.

Example 9 Preparation of Powdery Coating Composition

80 parts of a styrene-acrylic copolymer resin (Himer Uni-3000, softeningpoint: 98° C., manufactured by Sanyo Chemical Industry Co.) and 20 partsof fine particles of hydrophilic silica (Mizukasil P-527, averageparticle diameter: 1.6 μm, manufactured by Mizusawa Chemical IndustryCo.) were melt-kneaded. After cooling, the resulting mixture was groundand classified to obtain a hydrophobic resin powdery coating compositionhaving an average particle diameter of 11.0 μm. 100 parts of thishydrophobic resin powdery coating composition and 5 parts of fineparticles of hydrophilic silica (200, average particle diameter: 12 nm,manufactured by Nippon Aerosil Co.) were mixed by stirring to obtain apowdery mixture.

Production of Image-receiving Sheet for an Ink-jet Recording

Using a commercially available electrostatic spray device, the abovepowdery mixture was sprayed on the entire surface of a commerciallyavailable ordinary paper and the powdery mixture was heated to about 80to 100° C. under pressure, thereby to fix the powdery mixture to theordinary paper. At the same time, particles of powdery coatingcomposition were fused to each other, partially, to form a resin layerhaving a thickness of 20 μm, having a space between the particles ofpowdery coating composition, as an ink-receiving layer. Thus, animage-receiving sheet for an ink-jet recording was obtained.

Then, fine particles of hydrophilic silica (Aerosil 3.80, averageparticle diameter: 7 nm, manufactured by Nippon Aerosil Co.) weresprayed on this ink-receiving layer and the fine particles ofhydrophilic silica were heated to about 80 to 100° C. under pressure,thereby to fix a surface layer having a thickness of 3 μm made of theparticles of the hydrophilic silica on the ink-receiving layer, thusobtaining an image-receiving sheet for an ink-jet recording.

Ink-jet Recording Characteristics

Using a commercially available ink-jet printer (PM-750C, manufactured byEpson Co.), an ink-jet recording of the image-receiving sheet for anink-jet recording was performed, and then the absorbency and colordeveloping property of ink was examined. The absorbency of ink wasexamined as follows. A color chart defined by the Japanese StandardsSociety was ink-jet recorded on a recording paper and, immediately afterrecording, the image was touched by fingertip. The case where ink wasnot adhered to the fingertip was rated “good”, while the case where inkwas partially adhered to the fingertip was rated “poor”. The colordeveloping property of ink was examined by measuring the density of themost dense portion using a Macbeth densitometer (model RD-914). Theresults are shown in Table 2.

TABLE 2 Image Density Absorbency Yellow Magenta Cyan Black Example 6Good 1.10 1.13 0.61 1.49 7 Good 1.11 1.13 0.59 1.48 Comparative Poor0.80 0.83 0.40 1.11 Example 4 Example 8 Good 1.12 1.15 0.59 1.48 9 Good1.20 1.19 0.65 1.49

Example 10 Preparation of Powdery Coating Composition and PowderyMixture

100 parts of a styrene-acrylic copolymer resin (Himer Uni-3000,softening point: 98° C., manufactured by Sanyo Chemical Industry Co.)and 30 parts of polyethylene oxide polypropylene oxide (CP-2000manufactured by Sumitomo Seika Co.) as a water-soluble resin weremelt-kneaded in a double-screw melt-kneader at 150-160° C. for 4minutes. After cooling, the resulting mixture was ground and classifiedto obtain a white powdery coating composition having an average particlediameter of 11.0 μm. 95 parts of this white powdery coating compositionand 5 parts of hydrophilic anhydrous silica (Aerosil 200, averageparticle diameter: 12 nm, manufactured by Nippon Aerosil Co.) were mixedto obtain a white powdery mixture (proportion of anhydrous silica: 5%)for dry coating by an electrostatic spray method.

Production of Image-receiving Sheet for an Ink-jet Recording

Using a commercially available electrostatic spray device, the abovewhite powdery mixture was adhered on the entire surface of acommercially available ordinary paper, followed by melting by heatingand further fixing to form an image-receiving layer having a thicknessof 20 μm, thus obtaining an image receiving sheet for ink-jet recording.

Ink-jet Recording Characteristics

Using a commercially available ink-jet printer (PM-750C, manufactured byEpson Co.), an ink-jet recording of the image-receiving sheet for anink-jet recording was performed, and then the absorbency and colordeveloping property of ink was examined. The absorbency of ink wasexamined as follows. A color chart defined by the Japanese StandardsSociety was ink-jet recorded on a recording paper and, immediately afterrecording, the image was touched by fingertip. The case where ink wasnot adhered to the fingertip was rated “good”, while the case where inkwas partially adhered to the fingertip was rated “poor”. The colordeveloping property of ink was examined by measuring the density of themost dense portion using a Macbeth densitometer (model RD-914). Theresults are shown in Table 3.

Example 11

In the same manner as in Example 10, except that polyvinyl alcohol(PVA-117, manufactured by Kuraray Co.) was used in place of polyethyleneoxide polypropylene oxide as the water-soluble resin, a white powderymixture (proportion of anhydrous silica: 5%) was prepared, and then animage-receiving sheet for an ink-jet recording having a receiving layerhaving a thickness of 20 μm on a commercially available ordinary paperwas prepared by using the white powdery mixture. After ink-jet recordingwas performed, the absorbency and color developing property of ink wasexamined in the same manner as in Example 10. The results are shown inTable 3.

Example 12

In the same manner as in Example 10, except that hydroxylethylcellulose(AH-15, manufactured by Sumitomo Seika Co.) was used in place ofpolyethylene oxide polypropylene oxide as the water-soluble resin, awhite powdery mixture (proportion of anhydrous silica: 5%) was prepared,and then an image-receiving sheet for an ink-jet recording having areceiving layer having a thickness of 20 μm on a commercially availableordinary paper was prepared by using the white powdery mixture. Afterink-jet recording was performed, the absorbency and color developingproperty of ink was examined in the same manner as in Example 10. Theresults are shown in Table 3.

TABLE 3 Image Density Example Absorbency Yellow Magenta Cyan Black 10Good 1.14 1.17 0.63 1.52 11 Good 1.12 1.15 0.62 1.51 12 Good 1.13 1.160.62 1.50

What is claimed is:
 1. A sheet comprising a substrate and a resin layerfixed on the substrate, wherein the resin layer is formed of particlesof a resin containing powdery coating composition having an averageparticle diameter of 0.1 to 30 μm which are covered with inorganic fineparticles having an average particle diameter of 1 nm to 1 μm heated andpartially melted so that the particles of the partially melted powderycoating composition are fixed on the substrate as a continuous resinlayer, with the inorganic fine particles intervening at least in partbetween the partially melted particles of powdery coating compositionand providing space at least in part between the partially meltedparticles of powdery coating composition.
 2. The sheet according toclaim 1 wherein the powder coating composition further comprises acolorant.
 3. The sheet according to claim 1 wherein the amount of theinorganic fine particles is within a range from 0.5 to 10% by weightbased on the total amount of the powdery coating composition and theinorganic fine particles.
 4. The sheet according to claim 1 wherein theinorganic fine particles are those of hydrophilic anhydrous silica,aluminum oxide, titanium dioxide or calcium carbonate.
 5. The sheetaccording to claim 1 wherein the resin is a hydrophobic resin or amixture of a hydrophobic resin and a hydrophilic resin.
 6. The sheetaccording to claim 1 wherein the substrate is a paper.
 7. Animage-receiving sheet for an ink-jet recording comprising a sheet coatedwith a powdery coating composition in any one of claims 1 to
 6. 8. Animage-receiving sheet for use in ink-jet recording comprising asubstrate and a resin layer fixed on the substrate and a surface layerfixed on the resin layer, wherein the resin layer is formed of particlesof a resin containing powdery coating composition having an averageparticle diameter of 0.1 to 30 μm which are covered with first inorganicfine particles having an average particle diameter of 1 nm to 1 μmheated and partially melted so that the particles of the partiallymelted powdery coating composition are fixed on the substrate as acontinuous resin layer with the first inorganic fine particlesintervening at least in part between the particles of partially meltedpowdery coating composition and providing space at least in part betweenthe particles of partially melted powdery coating composition, and thesurface layer comprising second inorganic fine particles having anaverage particle diameter of 1 to 50 nm.
 9. The image-receiving sheetaccording to claim 8 wherein the amount of the first inorganic fineparticles is within a range from 0.5 to 10% by weight based on the totalamount of the powdery coating composition and the first inorganic fineparticles.
 10. The image-receiving sheet according to claim 8 or 9wherein the first inorganic fine particles are those of hydrophilicanhydrous silica, aluminum oxide, titanium dioxide or calcium carbonate.11. The image-receiving sheet according to claim 8 wherein the secondinorganic fine particles are those of hydrophilic anhydrous silica,aluminum oxide, titanium dioxide or calcium carbonate.